W-2 Form Explained: Every Box, and What to Verify

The most confusing thing about a W-2 is that Boxes 1, 3, and 5 are all "wages" and rarely match. Each box applies different rules to the same paychecks: Box 1 subtracts pre-tax retirement and cafeteria-plan benefits, Box 3 ignores retirement deferrals but caps at the Social Security wage base, and Box 5 ignores the cap entirely.

Read correctly, the differences are a free audit of your own payroll year: they reveal exactly what you deferred, what benefits cost, and whether anything was misreported. Read carelessly, they cause real errors, like typing Box 3 into a Box 1 field and overstating income.

This guide walks the form box by box, shows the reconciliation with a worked example, and flags what to verify before filing. For individual Box 12 and Box 14 codes, our dedicated code pages carry the full lists.

Boxes 7 through 11 cover narrower situations: tip income, dependent care benefits, and distributions from nonqualified deferred compensation plans. If Box 11 has an amount, the return needs care, because nonqualified plan distributions follow their own reporting path.

Take a $200,000 salary with a maxed 2026 401(k) deferral of $24,500 and $6,000 of pre-tax health premiums. Each wage box applies its own rules.

The reconciliation habit pays off beyond error-catching. Box 1 versus Box 5 measures your pre-tax income deferrals; Box 3 hitting exactly $184,500 confirms you maxed the Social Security base; Box 2 divided by Box 1 is your average federal withholding rate, a one-line sanity check against the liability a projection expects. Five minutes with these ratios each January tells you whether the coming filing season holds surprises.

Box 12 compresses the interesting payroll items into letter codes. The ones high earners see most: D (pre-tax 401(k) deferrals), AA (Roth 401(k)), W (HSA contributions through the employer, both employer money and your payroll deferrals), DD (total cost of employer health coverage, informational only, not taxable), C (taxable group-term life insurance over $50,000), and V (income from exercising nonqualified stock options, also already inside Boxes 1, 3, and 5).

Two habits prevent the common errors. Confirm code W matches what you think went into your HSA before filing Form 8889, and never deduct code DD anywhere; it is disclosure, not income or deduction. Our Box 12 codes guide covers the full alphabet, including the rare ones.

Retirement codes also deserve a year-end check against the limits: code D plus code AA across all employers should not exceed the $24,500 elective deferral limit for 2026 ($32,500 with the 50+ catch-up). Excess deferrals happen most often after a mid-year job change, when neither payroll knows about the other, and they must be distributed by the following April 15 to avoid double taxation.

Check the basics first: name and SSN exactly as on your Social Security card, all employers accounted for, and withholding that matches final pay stubs. Then check the equity items if you have them: RSU vest income should appear in Box 1 (often detailed in Box 14), and sell-to-cover share sales will also generate a 1099-B whose basis frequently needs adjustment so the same income is not taxed twice.

If a W-2 is wrong, the employer must fix it by issuing Form W-2c; you cannot correct it yourself on the return with different numbers and no paper trail. If the form is late or the employer unresponsive, the IRS can be asked to intervene, and Form 4852 serves as a substitute W-2 built from your pay stubs.

Multi-state workers should scrutinize Boxes 15 to 20. Employers allocate wages among states based on their records of where you worked; locum physicians and remote employees routinely find allocations that do not match reality, and the state lines drive state filing obligations.

S-corp owners have one W-2 item of their own: health insurance premiums paid for a more-than-2% shareholder belong in Box 1 wages (not Boxes 3 and 5) and are typically noted in Box 14. Missing that entry is common with new payroll providers, and it breaks the owner’s self-employed health insurance deduction downstream, which keys off the W-2 reporting.

Timing errors are their own category. Wages are reported in the year paid, not earned, so a December bonus paid in January belongs on next year’s W-2, and a final paycheck after a year-end departure can land a year later than expected. Repayments run the other direction: sign-on bonus clawbacks repaid in a later year cannot simply reduce that year’s W-2; they follow the claim-of-right rules on your return instead. When a W-2 looks wrong by exactly one payment, check the pay date before requesting a correction; more often than not, the form is right and the calendar is the explanation.

Equity compensation is where W-2 reading earns its keep. When RSUs vest, the fair market value of the shares lands in Boxes 1, 3 (up to the wage base), and 5 as ordinary wages, with the withholding, typically the flat 22% supplemental rate, folded into Box 2. Many employers itemize the vest amount in Box 14, which is informational but invaluable for reconciliation.

Walk one vest: $50,000 of RSUs vest in June. Box 1 includes the $50,000; Box 2 includes roughly $11,000 of federal withholding on it at 22%. The company sells or withholds shares to cover, and the broker later issues a 1099-B for any sale. Here is the trap: the broker frequently reports the basis of those shares as zero or omits it, because the basis was established through payroll, not through the brokerage. Without an adjustment, the $50,000 appears again as capital gain.

The fix is mechanical: adjust the basis on Form 8949 to the vest-date value already taxed through the W-2, so only the price movement between vest and sale is gain or loss. The Box 14 detail, the vest confirmations, and the final pay stub are the documents that prove the adjustment. Nonqualified stock option exercises follow the same pattern, flagged with code V in Box 12.

For a high earner, this one reconciliation is routinely worth more than everything else on the form: the double-tax error on a six-figure vest is a five-figure overpayment, silent unless someone matches the W-2 to the 1099-B.